|Year : 2019 | Volume
| Issue : 3 | Page : 267-270
A rare phenomenon of twin spotting: Phacomatosis pigmentokeratotica
Vaishali Wankhade, Vrutika Hasmukh Shah, Rajesh P Singh, Jayesh Mukhi
Department of Dermatology, Venereology and Leprosy, Government Medical College, Nagpur, Maharashtra, India
|Date of Web Publication||28-Jun-2019|
Dr. Vrutika Hasmukh Shah
B.1103, Apollo Pride Enclave Complex, Next to Thane Bharat Sahakari Bank, Baji Prabhu Deshpande Marg, Vishnunagar, Thane West, Thane - 400 602, Maharashtra
Source of Support: None, Conflict of Interest: None
Phacomatosis pigmentokeratotica is a rare form of cutaneous mosaicism characterized by epidermal nevus usually nevus sebaceous, papular speckled lentiginous nevus, and extracutaneous anomalies. This type of twin-spot phenomenon (didymosis) is due to postzygotic crossing-over resulting in two homozygous daughter cells, representing the stem cells of the two distinct types of nevi and leading to additional extracutaneous defects. We report a case of this rare syndrome in a 4-year-old male child associated with skeletal anomalies.
Keywords: Cutaneous mosaicism, nevus sebaceous, skeletal, speckled lentiginous nevus, twin-spot phenomenon
|How to cite this article:|
Wankhade V, Shah VH, Singh RP, Mukhi J. A rare phenomenon of twin spotting: Phacomatosis pigmentokeratotica. Indian J Paediatr Dermatol 2019;20:267-70
|How to cite this URL:|
Wankhade V, Shah VH, Singh RP, Mukhi J. A rare phenomenon of twin spotting: Phacomatosis pigmentokeratotica. Indian J Paediatr Dermatol [serial online] 2019 [cited 2019 Sep 19];20:267-70. Available from: http://www.ijpd.in/text.asp?2019/20/3/267/261883
| Introduction|| |
Phacomatosis pigmentokeratotica (PPK) is an example of twin spotting, which is made up of two components which are Schimmelpenning syndrome and speckled lentiginous nevus (SLN) syndrome., The Schimmelpenning syndrome is characterized by linear nevus sebaceous and extracutaneous involvement, including skeletal, neurologic, and ocular abnormalities. PPK shares the nevus sebaceous with the Schimmelpenning syndrome, but it differs from the latter in the presence of SLN and the absence of major central nervous system effects, along with conjunctival lipodermoid or coloboma., The most frequently associated extracutaneous alterations of PPK are neurologic (hemiatrophy with muscular weakness, hyperhidrosis, and dysesthesia in the region of the SLN), ophthalmologic (strabismus and ptosis), and skeletal disorders (kyphosis and scoliosis).
| Case Report|| |
A 4-year-old male child born out of nonconsanguineous marriage presented with dark-colored lesions over the right temporal area, shoulder, and upper extremity. History of delayed milestones with inability to walk was present. Antenatal, birth, and family histories were unremarkable. Cutaneous examination revealed multiple, yellowish-brown hyperkeratotic velvety plaques following Blaschko's lines over the right side of the face, extending to the scalp leading to localized alopecia on the right temporal area, postauricular region, and neck [Figure 1]a. A large light brown patch extending unilaterally from the right side of the scalp, to the neck, chest, axilla, upper back, and right upper limb was seen, overlying which were multiple small brownish-black macules and papules [Figure 1]b. A clinical diagnosis of nevus sebaceous for right temporal and neck lesion and SLN for the right scalp, trunk, and upper limb lesions was done. On systemic examination, the patient had kyphoscoliosis along with bowing of the legs. Histopathology of right neck lesion revealed papillomatous epidermal hyperplasia, enlarged sebaceous lobules, and buds of follicular germinative cells along the dermoepidermal junction, suggestive of nevus sebaceous [Figure 2]a and [Figure 2]b. Histopathology of right arm lesion revealed an increased number of melanocytes in the superficial epidermis with hyperpigmentation of the basal epidermis corresponding to the patch and nests of melanocytes in the dermis corresponding to the speckles, suggestive of SLN [Figure 3]a and [Figure 3]b. Radiological examination of the upper and lower limbs revealed limb dysplasia. X-ray of the spine anteroposterior and lateral views revealed kyphoscoliosis [Figure 4]a and [Figure 4]b. X-ray of the brain showed widening of the sella turcica and calvarial thinning involving the skull vault [Figure 5]. X-ray of the bilateral forearm and left leg revealed diffuse osteopenia and cortical thinning (blue arrows), pathological fractures (red arrows), and widening of growth plate involving left knee joint (yellow arrow); all the above features were suggestive of rickets [Figure 6]a, [Figure 6]b, [Figure 6]c. Plain magnetic resonance imaging of the brain was normal. Hematological investigations revealed low serum phosphate (1.7 mg/dL), high alkaline phosphatase (835 U/L), and normal serum calcium, parathyroid hormone, and Vitamin D3 levels. HRAS mutation analysis was considered, but could not be done due to paucity of resources. Based on the clinical, histopathological, radiological, and hematological findings, a diagnosis of PPK with kyphoscoliosis and hypophosphatemic rickets was made. The patient was referred to pediatrics and orthopedics for management of skeletal anomalies and plastic surgery for management of nevus sebaceous. The patient was immobilized with a cast along with Vitamin D3 and phosphate therapy and 6-month posttherapy healing of the fracture was observed. X-ray of the right forearm showed healing of pathological fracture [Figure 6]d.
|Figure 1: (a) Multiple brown hyperkeratotic velvety plaques along with localized alopecia in blaschkoid pattern (yellow arrow). (b) A well-defined light brown patch with overlying multiple small brownish-black macules and papules in segmental distribution (red arrows)|
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|Figure 2: (a) Right neck lesion showing papillomatous epidermal hyperplasia (red arrow), focal hyperpigmentation in the basal layer (black arrow) and numerous dilated pilosebaceous structures in the dermis (green arrow) (H and E, ×10). (b) Buds of follicular germinative cells along the dermoepidermal junction (brown arrow) (H and E, ×40)|
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|Figure 3: (a, H and E, x10 & b, H and E, x40) Right arm lesion showing increased number of melanocytes in the superficial epidermis with hyperpigmentation of the basal epidermis (black arrow) corresponding to patch and nests of melanocytes in the dermis (red arrows) corresponding to speckles|
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|Figure 4: (a) Anteroposterior view and (b) lateral view: X-ray spine: Kyphoscoliosis with dextroscoliosis in the thoracic spine (yellow arrow) and levoscoliosis in the lumbar (red arrow)|
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|Figure 5: X-ray brain lateral view: Widening of the sella turcica (blue arrow) and calvarial thinning involving the skull vault|
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|Figure 6: X-ray anteroposterior view of (a) left forearm, (b) left leg, (c) right forearm: Diffuse osteopenia and cortical thinning (blue arrows), pathological fractures (red arrows), and widening of growth plate involving left knee joint (yellow arrow); all the above features are suggestive of rickets, and (d) X-ray anteroposterior view of the right forearm: Post 6-month therapy X-ray-healing of pathological fracture (white arrow)|
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| Discussion|| |
PPK was first described by Happle based on a series of some patients characterized by the coexistence of organoid nevi with sebaceous differentiation, arranged along the Blaschko's lines, along with SLN in a checkerboard pattern. It was considered to represent an example of twin spotting or didymosis, which is why it has also been called “didymosis spilosebacea.” Twin-spot phenomenon (didymosis) is due to postzygotic crossing-over resulting in two homozygous daughter cells, representing the stem cells of the two distinct types of nevi and of the additional extracutaneous defects. However, recent reports have shown that the paired nevi originate from one single multipotent progenitor cell being heterozygous for an HRAS mutation and hence the theory of didymosis can no longer be upheld and should be regarded as “pseudodidymosis.”, This theory is true for some of the other proposed examples of nonallelic twin spotting, such as phacomatosis cesioflammea and phacomatosis spilorosea. The concept of allelic didymosis as proposed for the paired occurrence of nevus flammeus and nevus anemicus, mixed vascular nevus syndrome, and cutis tricolor will be corroborated by molecular studies.
The male-to-female ratio of PPK is 2.4:1. PPK is divided into two subgroups by the presence or absence of systemic involvement. The various systemic and other associations with PPK have been described in [Table 1]., The most common systemic involvement reported is hemiatrophy. In our patient, skeletal anomalies in the form of kyphoscoliosis and hypophosphatemic rickets were present. The pathogenic mechanism associated with the onset of hypophosphatemic rickets in patients with epidermal nevus syndrome (ENS) remains unknown, but it is considered variant of tumor-induced rickets because the excision of bone and soft-tissue mesenchymal tumors associated with hypophosphatemic rickets usually causes remission of the skeletal disease. Another theory for causal association between hypophosphatemic rickets and ENS is demonstrated by the presence of phosphaturic substance extracted from the skin lesions, and removal of the skin lesions leads to improvement of rickets. Few authors have also incriminated that angiomas found within the sebaceous nevi or the bones of patients with ENS act as the probable secretors of an endocrine factor causative of rickets. There are various stages of organoid nevi. The first stage is characterized by alopecia with absent or primitive hair follicles and numerous small hypoplastic sebaceous glands. At puberty, lesions become verrucous with hyperplastic sebaceous glands. Benign or malignant tumors develop at later stages. Patients must be monitored for the occurrence of trichoblastoma in the organoid nevi on an epidermal twin nevus syndrome.
There is no causal therapy of PPK. Potential methods for a symptomatic improvement of the lesions are dermabrasion, excision, or laser therapy. The presence of extracutaneous manifestations warrants a detailed investigation of such patients to rule out systemic anomalies. Also, adequate patient follow-up care should be taken to ensure early detection of possible associated malignant change within the pigmented lesions and the epidermal nevus in later life.
Here, we report a case of PPK with skeletal disorders (kyphoscoliosis and hypophosphatemic rickets). This case is atypical as it presents SLN in segmental pattern instead of the characteristic checkerboard pattern. To summarize, patients presenting with two nevi should undergo a detailed systemic examination to rule out extracutaneous involvement, which may be treatable as in our case who was treated for rickets which gave him a better quality of life.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the parent has given his/her consent for images and other clinical information to be reported in the journal. The parent understands that name and initial will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]